Methods for the treatment or prophylaxis of thrombosis or embolism

ABSTRACT

The present invention relates to a method of ameliorating the drawbacks of anti-platelet drug named clopidogrel. The method of the present invention comprises administration of an (S)oxo-clopidogrel or its derivative of the Formula IIA in its free or pharmaceutically acceptable salt form for alleviating the symptoms of thrombosis or embolism by inhibiting blood platelet aggregation. Compositions for use in such methods are also provided.

This application claims the priority of Indian Patent Application No.2388/MUM/2010, filed Aug. 26, 2010, which is incorporated herein byreference.

FIELD OF INVENTION

The present invention relates to treatment or prophylaxis of thrombosisor embolism. The present invention ameliorates the drawbacks ofantiplatelet drugs, such as clopidogrel, by using an (S)-oxo-clopidogrelor its derivative, in its free or pharmaceutically acceptable salt formfor alleviating the symptoms of thrombosis and/or embolism by inhibitingblood platelet aggregation.

BACKGROUND OF THE INVENTION

Conditions resulting from thrombotic or thromboembolic events are theleading causes of illness and death in adults in western civilization.Intravascular thrombosis and embolism are common clinical manifestationsof many diseases. Unregulated activation of the hemostatic system hasthe potential to cause thrombosis and embolism, which can reduce bloodflow to critical organs like the brain and myocardium. Certain patientgroups have been identified that are particularly prone to thrombosisand embolism. These include patients (1) immobilized after surgery, (2)with chronic congestive heart failure, (3) with atherosclerotic vasculardisease, (4) with malignancy, or (5) who are pregnant. The majority of“thrombosis prone” individuals have no identifiable hemostatic disorder,although there are certain groups of individuals having inherited oracquired “hypercoaguable” or “prethrombotic” conditions predisposingthem to recurrent thrombosis (Harrison's Principles of InternalMedicine, 12th ed. McGraw Hill).

Effective primary hemostasis requires three critical events: plateletadhesion, granule release, and platelet aggregation. Within a fewseconds of injury, platelets adhere to collagen fibrils in vascularsubendothelium. This interaction is facilitated by von Willebrandsfactor, an adhesive glycoprotein which allows platelets to remainattached to the vessel wall despite the high shear forces generatedwithin the vascular lumen. Von Willebrand's factor accomplishes thistask by forming a link between platelet receptor sites andsubendothelial collagen fibrils.

As the primary hemostatic plug is being formed, plasma coagulationproteins are activated to initiate secondary hemostasis. There is littledifference between hemostatic plugs, which are a physiological responseto injury, and pathologic thrombi. Thrombosis is often described ascoagulation which has occurred in the wrong place or at the wrong time.Hemostatic plugs or thrombi that form in veins where blood flow is sloware richly endowed with fibrin and trapped red blood cells and containrelatively few platelets. These thrombi often form in leg veins and canbreak off and embolize to the pulmonary circulation. Conversely, clotsthat form in arteries under conditions of high flow are predominantlycomposed of platelets and have little fibrin. These arterial thrombi mayreadily dislodge from the arterial wall and embolize to distant sites tocause temporary or permanent ischemia. This is particularly common inthe cerebral and retinal circulation and may lead to transientneurologic dysfunction (transient ischemic attacks) including temporarymonocular blindness (amaurosis fugax) or strokes. In addition, there isincreasing evidence that most myocardial infarctions are due to thrombiwhich form within atherosclerotic coronary arteries. (The precedingdiscussion is taken primarily from Harrison's Principles of InternalMedicine, 12th ed., McGraw Hill.)

Extracellular nucleotides and their receptors of platelets are importantcomponents of the cardiovascular system and are involved in functionslike platelet activation and the control of vascular tone. Adenosinediphosphate (ADP) and Adenosine Triphosphate (ATP), are playing crucialroles in the physiological process of haemostasis and in the developmentand extension of arterial thrombosis (2). By itself ADP is a weakagonist of platelet aggregation inducing only reversible responses ascompared to strong agonists such as thrombin or collagen. However, dueto its presence in large amounts in the platelet dense granules and itsrelease upon activation at sites of vascular injury, ADP is an importantso-called secondary agonist which amplifies most of the plateletresponses and contributes to the stabilization of the thrombus. Thereceptors for extracellular nucleotides belong to the P2 family whichconsists of two classes of membrane receptors: P2X ligand-gated cationchannels (P2×1-7) and Glycoprotein-coupled P2Y receptors (P2Y1, 2, 4, 6,11, 12, 13, 14). Each of these receptors has a specific function duringplatelet activation and aggregation, which naturally has implicationsfor their involvement in thrombosis.

Since ADP and ATP play a crucial role in platelet activation, theirreceptors are potential targets for antithrombotic drugs. The ATP-gatedcation channel P2X1 and the two G protein-coupled ADP receptors, P2Y1and P2Y12, selectively contribute to platelet aggregation and formationof a thrombus. Owing to its central role in the growth and stabilizationof a thrombus, the P2Y12 receptor is an established target ofantithrombotic drugs mainly the thienopyridine class of compounds liketiclopidine, clopidogrel, prasugrel etc. . . . .

The mainstay of antiplatelet therapy for patients with acute coronarysyndromes (ACS), including those undergoing early percutaneous coronaryintervention (PCI) and stents implantation is administration of acombination of Aspirin and clopidogrel. Aspirin inhibits plateletthomboxane A2 production and platelet activation, and reduces the riskof recurrent ischemic events in patients at high risk of vascular eventsby 22% (absolute risk reduction (ARR) about 2%) at the expense of anincrease in the odds of major bleeding events by about 60% (Absoluterisk increase (ARI) about 0.5%. Clopidogrel inhibits ADP inducedplatelet activation by blocking the platelet receptor P2Y12, which whencombined with Aspirin therapy in patients with ACS, reduces the risk ofrecurrent ischemic events by a further 20% (ARR about 2.1%), in whichthe major bleeding events are not increased statistically from aspirinmonotherapy.

Clopidogrel (Formula I), chemically named as “(+)-(S)-methyl2-(2-chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl)acetate”,is currently considered to be the gold standard in the inhibition ofblood platelet aggregation. Clopidogrel is marketed as its hydrogensulphate, hydrochloride, and benzene sulphonate salts. It is widely usedfor controlling the ischemic events and other cardiovascular disordersefficiently for last 12 years or more.

However, clopidogrel has several potential limitations. First, the onsetof action is delayed and a time lag between administration andtherapeutic activity is observed. A therapeutically significant level of50% inhibition of ADP induced platelet aggregation, as measured by lighttransmission aggregometry (LTA) (5 μM ADP ex-vivo) is not reached until4-6 hours after administration of a loading dose of 300 mg clopidogrelor until 2 hours by doubling the dose to 600 mg. Secondly, there is adose ceiling effect, as tripling the dosing from regular dose of 300 mgto 900 mg produces only 60% inhibition of ADP induced plateletaggregation (at 5 μM ADP), and less than 50% inhibition of plateletaggregation (induced by 20 μM of ADP (ex vivo)). Third, almost allclinical trials involving clopidogrel reveal that therapeutic levels ofplatelet inhibition are not achieved in a majority of patients becauseof large inter-individual variability in response to clopidogreltreatment. This patient population is referred as ‘non-responders’ or‘poor responders’ to clopidogrel. Non-responders make up about 14% ofthe ethnic Chinese population and 3-4% among Caucasians. Overall, poorresponders are close to 23% of the total patient population, andvariation of inhibitory activity is reported in about 45% of the totalpatient population. The ultrarapid metabolism of clopidogrel has beenreported in patients having a specific phenotype of CYP isoform (about4%-18% patients) which leads to more severe bleeding episodes, withhigher platelet aggregation. Considering these facts and data fromclinical trials, the FDA requires that a boxed warning be included inthe label of clopidogrel highlighting the ineffectiveness of clopidogrelin certain classes of patients and suggesting screening of patients forgenotyping to identify poor responders to clopidogrel before treatment.

It has been found that the variations in the inhibitory activity ofclopidogrel originates from the difference in the activity of liverenzymes that metabolize clopidogrel. Upon ingestion of clopidogrel, itundergoes a series of metabolic reactions to produce metabolites. Thesereactions are mediated by CYP 450 as well as by action of hepatic humancarboxyl esterase (hCE). The metabolic pathway of clopidogrel is set outbelow. The use of the specific metabolites as therapeutic agents foradministration to patients in place of clopidogrel has not beensuggested previously.

As an alternative to clopidogrel, prasugrel can also be used. However,treatment of patients with prasugrel rendered them susceptible tobleeding episodes, which may be life threatening, restricting itsapplication in patients having a body weight of less than 60 kg bodyweight and greater than 75 years of age. Prasugrel has also been foundto increase liver disease/toxicity in patients who are at risk ofcirrhosis and thus pharmacovigilance is suggested by the FDA. As far asthese severe side effects are concerned, clopidogrel is comparativelysafer, resulting generally in lesser bleeding and liver toxicity.Further, the incidence of cardiovascular deaths is greatly reducedfollowing treatment with clopidogrel in comparison to prasugrel and thusimprovements in the efficacy of clopidogrel are likely to reduce therisk of thrombosis and/or embolism in patient groups much better thanother structurally modified drugs.

Due to the serious side effects, including the risk of bleeding,associated with the use of prasugrel, it is recommended that prasugrelonly be used to achieve an initial thrust of greater inhibition ofplatelet aggregation. Clopidogrel is then used for subsequent plateletinhibition, after the initial use of prasugrel.

Therefore, there is a need to ameliorate the side effects of clopidogrelor prasugrel. Compounds exhibiting higher onset of action, lowerinter-individual variability, better metabolizers status, improved doseceiling effect, and improved efficacy by increasing inhibitory capacityon ADP induced platelet aggregation are desired.

SUMMARY OF THE INVENTION

The present inventors have discovered that the use of clopidogrelpresents substantial clinically significant limitations in inhibitingplatelet aggregation safely and rapidly in a consistent manner, thoughit is considered to be the gold standard among anti-platelet medicineavailable today. The invention, therefore, aims to provide improvedmethods for treatment/prophylaxis of thrombosis and embolism, as well ascompositions for use in such methods, which ameliorate at least one ofthe clinical drawbacks of clopidogrel discussed above.

In accordance with a first aspect, the invention provides a method oftreatment and/or prophylaxis of thrombosis and/or embolisms in a patientin need of such treatment, while avoiding and/or alleviating the sideeffects associated with the clopidogrel acid metabolite of Formula IVcomprising administering an amount of (S)-oxo-clopidogrel (Formula II)or its derivatives or a pharmaceutically acceptable salt thereof. In anembodiment isolated (S)-oxo-clopidogrel or its derivatives or apharmaceutically acceptable salt thereof is administered.

In preferred embodiments of this aspect of the present invention, themethod achieves a therapeutic effect greater or equivalent to thatobserved following the administration of a substantially higher dose ofclopidogrel.

According to a second aspect of the present invention, there is provideda method of treatment and/or prophylaxis of thrombosis and/or embolismsin a patient in need of such treatment while avoiding and/or alleviatingthe side effects associated with the clopidogrel acid metabolite ofFormula IV comprising administering an amount of the (S)-oxo-metaboliteof clopidogrel or its derivatives or a pharmaceutically acceptable salt.

In preferred embodiments of this aspect of the present invention, themethod results in the in vivo formation of the active metabolite ofclopidogrel at a concentration greater than or equivalent that observedfollowing administration of a substantially higher dose of clopidogrel.

According to a third aspect of the present invention, there is providedan improved method for delivering the active clopidogrel metabolite invivo for the treatment and/or prophylaxis of thrombosis and/or embolismsin a human in need of such treatment while avoiding or alleviating theside effects associated with inactive clopidogrel acid metabolite ofFormula IV, wherein the improvement consists essentially ofadministering an amount of (S)-oxo-metabolite of clopidogrel or itsderivatives or a pharmaceutically acceptable salt.

In all aspects of the present invention, the onset of therapeutic actionis at least 50% more rapid than that observed following administrationof a substantially higher dose of clopidogrel.

Further, in all aspects of the present invention, various amounts of theoxo-metabolite of clopidogrel or its derivative of Formula IIA may beadministered. For example, the amount administered may be 20 to 60 mgand the substantially higher dose of clopidogrel may be 300 mg.Alternatively, the amount of oxo-metabolite or its derivative of FormulaIIA may be 35 to 80 mg and the substantially higher dose of clopidogrelmay be 600 mg. In alternative embodiments, the amount of oxo-metaboliteor its derivative of Formula IIA may be 50 to 100 mg and thesubstantially higher dose of clopidogrel may be 900 mg. In still furtherembodiments, the amount of oxo-metabolite or its derivative of FormulaIIA may be 5 to 15 mg and the substantially higher dose of clopidogrelmay be 75 mg. Alternatively, the amount of oxo-metabolite or itsderivative of Formula IIA may be 6 to 20 mg and the substantially higherdose of clopidogrel may be 150 mg.

As an alternative to therapy involving the administration of a series ofrepeated doses to a patient, a higher loading dose may be followed byone or more maintenance doses. For example, a loading dose of 30-60 mgoxo-clopidogrel or its derivative of Formula IIA may be administered toa patient resulting in greater than 50% inhibition of ADP induced humanblood platelet aggregation. In certain embodiments of the presentinvention, this, or an alternative loading dose may be followed with amaintenance dose of 6-25 mg oxo-clopidogrel or its derivative of FormulaIIA is administered to a patient, resulting in greater than 50%inhibition of ADP induced human blood platelet aggregation. The dosesdiscussed herein are for a patient of 60 kg average body weight. Itshould be understood that dose may be adjusted with respect to bodyweight of the patient, health/condition condition of the patient,severity of the disease, metabolic profile of the compounds of thepresent invention. The skilled person in the art has the ability andexpertise to adjust the dosage as required.

According to a fourth aspect of the present invention, there is provideda method for minimizing inter individual platelet reactivity variabilityand metabolic loading in the treatment and/or prophylaxis of thrombosisand/or embolisms observed following administration of a dose ofclopidogrel said method comprising administering an effective amount(S)-oxo-clopidogrel metabolite or its derivatives or a pharmaceuticallyacceptable salt to a patient in need thereof.

The inter-individual variability may be due to CYP450 isoforms and itspolymorphic manifestations, for example, in the CYP2C19*2 allele orCYP2C19*17 allele. Additionally or alternatively, the inter-individualvariability may be due to P-glycoprotein efflux transports. As such, inan embodiment, the (S)-oxo-clopidogrel is administered to an individualhaving a CYP450 polymorphism that may cause clopidogrel resistance.Preferably, the CYP450 polymorphism is CYP2C19*2, *1, *2, *3, *4, *5,*6, *7, *8, *9, *10, and/or *17; more preferably CYP2C19*2 and/or *17;and most preferably CYP2C19*2.

According to a fifth aspect of the present invention, there is provideda method for the treatment or prophylaxis of thrombosis or embolismscomprising administration of (S)-oxo-clopidogrel metabolite or itsderivatives or a pharmaceutically acceptable salt and a proton pumpinhibitor.

In all aspects of the present invention, the methods discussed hereinmay additionally comprise the step of administration of one or moreadditional therapeutic agents. These may include, for example,anti-platelet agents selected from aspirin, cilostazol and dipyridamole.These additional agents may be administered simultaneously, sequentiallyof subsequently to the principal active ingredient.

According to a sixth aspect of the present invention, there are providedcompositions for use in the methods described herein. For the avoidanceof any doubt, where reference is made to the administration of an amountof active ingredient, this may be comprised within the composition ofthis aspect of the invention.

According to a seventh aspect of the present invention, there isprovided a fixed dose composition of (S)-oxo-clopidogrel or itsderivative of Formula IIA characterized in that said compositioncomprises a dose of 5-35 mg of oxo-clopidogrel or its derivative ofFormula IIA.

In a preferred aspect of the present invention, the fixed dosecomposition comprises a dose of oxo-clopidogrel or its derivative ofFormula IIA of 5-15 mg. The fixed dose composition may additionally oralternatively further comprise one or more anti-platelet agents selectedfrom aspirin, cilostazol and dipyridamole.

The advantages of the present invention are realized through use ofcompounds of Formula II or Formula IIA as well as salts or tautomersthereof

where R is a hydrogen or a hydrolysable group, such as acyl or alkylsubstituted silyl group. The term “acyl” refers to a functional grouphaving the general formula R¹—CO—, where R¹ can be a aryl, alkyl,alkenyl, or alkynyl. The preferred acyl group is acetyl. The term “alkylsubstituted silyl” refers to a functional group having the generalformula R′₃—Si—, where each of R′ is an alkyl. The term “alkyl” refersto a straight or branched hydrocarbon chain radical consisting solely ofcarbon and hydrogen atoms, containing solely carbon and hydrogen atoms,containing no unsaturation, having, preferably, from one to eight carbonatoms, and which is attached to the rest of the molecule by a singlebond, such as illustratively, methyl, ethyl, n-propyl, 1-methylethyl(isopropyl), n-butyl, n-pentyl, and 1,1-dimethylethyl (t-butyl). Theterm “alkenyl” refers to an aliphatic hydrocarbon group containing acarbon-carbon double bond and which may be a straight or branched orbranched chain having, preferably, about 2 to about 10 carbon atoms,e.g., ethenyl, 1-propenyl, 2-propenyl (allyl), iso-propenyl,2-methyl-1-propenyl, 1-butenyl, 2- and butenyl. The term “alkynyl”refers to a straight or branched chain hydrocarbonyl radicals having atleast one carbon-carbon triple bond, and having, preferably, in therange of about 2 up to 12 carbon atoms (with radicals having in therange of about 2 up to 10 carbon atoms being preferred), e.g., ethynyl.The term “aryl” refers to aromatic radicals, preferably, having 6 to 14carbon atoms such as phenyl, naphthyl, tetrahydronaphthyl, indanyl,biphenyl being optionally further substituted by an C₁-C₆ alkyl groupand/or a halogen atom.

The compound of Formula II is a metabolite of clopidogrel. Despite thestructure of this metabolite and its position in the metabolic pathwayof clopidogrel being known for almost 20 years, its use as an activeagent for the treatment of thrombosis and/or embolisms has notpreviously been suggested. For Example, a method for preparing such acompound as an intermediate for producing a purportedly efficaciousanalog of clopidogrel (rather than as an active ingredient in its ownright) is disclosed in Example 3 of WO2011/095049. The inventors haveidentified that the compound of Formula II (as well as itspharmaceutically acceptable salts, tautomers and derivatives of FormulaIIA) can advantageously be administered directly to patients in place ofclopidogrel and that this ameliorates some if not all of thedisadvantages associated with the use of clopidogrel.

This is partly because the metabolite identified as Formula IV in thepathway provided above has been found to be inactive. By administeringthe compound of Formula II to a patient, the inactive metabolite is notproduced in vivo. Further, one less CYP mediated step is required toconvert the compound of Formula II (as opposed to clopidogrel) to theactive metabolite. Thus, the influence that the patient's ability tometabolize has on efficacy is reduced.

As mentioned above, the use of metabolites of clopidogrel as activeagents in their own right, especially Formula II, has not previouslybeen taught or suggested for ameliorating the drawbacks of clopidogrel,and thus, the advantages of doing so, which are discussed herein cannothave been recognized.

The invention provides a method for treatment and/or prophylaxis ofthrombosis and/or embolism, where the method comprises administering apredetermined dose of an isolated (S)-isomer of thiolactone compound ofFormula II or its tautomer or a derivative thereof in its free form oras a pharmaceutically acceptable salt thereof such that it results inthe in vivo formation of the active metabolite of clopidogrel at aconcentration equivalent or greater than that achieved through theadministration of a substantially greater dose of clopidogrel. In apreferred embodiment, the present invention enables a substantialreduction in the dose of active ingredient required for achieving atherapeutic concentration of active metabolite of clopidogrel comparedwith administration of conventional, therapeutic doses of clopidogrel.Thus, dose tolerability and efficacy are enhanced significantly.

In another aspect, the present invention can deliver higherconcentrations of the active metabolite of clopidogrel in systemiccirculation shortly after administration compared to administeringclopidogrel. This not only improves the onset of therapeutic action byachieving greater than 50% inhibition of ADP induced plateletaggregation and inter individual variability, but also eliminates theside effects associated with the inactive acid metabolite (Formula IV)and reduces the metabolic load on liver.

In aspects of the present invention, one or more additional activecompounds may be administered including antiplatelet agents likeaspirin, cilostazol and the like. The antiplatelet agents may operate bya mechanism similar or different to the clopidogrel active metabolite toachieve desired levels of anti-platelet activity. The second orsubsequent anti-platelet agent may be administered separately,sequentially or simultaneously with the (S)-isomer of thiolactonecompound of Formula II (also referred to herein as (S)-oxo clopidogrel)or its tautomer or a derivative thereof in its free form or as apharmaceutically acceptable salt thereof.

In aspects of the present invention, a dose ranging from 20-100 mg ofcompound of Formula II or its tautomers or its derivative of Formula IIAmay be administered as an initial loading dose, and if necessary, amaintenance dose as low as 5-35 mg may subsequently be administered suchthat the systematic concentration of active metabolite is greater thanthat amount obtained by administering a loading dose of 300-900 mg and amaintenance dose of 75-150 mg of clopidogrel. More preferably theloading dose of the present invention is between 40-75 mg andmaintenance dose is between 6-25 mg. Still further lower doses may beadministered, if the desired inhibition is equivalent or slightlyinferior to that provided by clopidogrel. The doses discussed herein arefor a patient of 60 kg average body weight. It should be understood thatdose may be adjusted with respect to body weight of the patient,health/condition condition of the patient, severity of the disease,metabolic profile of the compounds of the present invention. The skilledperson in the art has the ability and expertise to adjust the dosage asrequired.

The derivative of Formula IIA may be made from the tautomer of thecompound of Formula II, which is preferably an ester (alkyl, aryl, orsilyl) derivative. More preferably the derivative is acylatedthiolactone of Formula VI.

In aspects of the present invention, there are provided compositions foruse in the methods discussed herein. For example, the present inventionprovides a fixed dose pharmaceutical composition comprising 5 mg to 35mg of the compound of Formula II or its tautomers or its derivative ofFormula IIA or a pharmaceutically acceptable salt thereof and optionallyone or more pharmaceutically acceptable excipients. The fixed dosecombination of the present invention may be administered along with oneor more active compound including antiplatelet agents like aspirin,cilostazol, PPIs (proton pump inhibitors, such as omeprazole), etc.,which may operate by a mechanism similar or other than clopidogrelactive metabolite.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Unless specified otherwise, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art, to which this invention belongs. Although any methodsand materials similar or equivalent to those described herein can beused in the practice or testing of the present invention, the preferredmethods and materials are described. To describe the invention, certainterms are defined herein specifically as follows.

Unless stated to the contrary, any of the words “including,” “includes,”“comprising,” and “comprises” mean “including without limitation” andshall not be construed to limit any general statement that it follows tothe specific or similar items or matters immediately following it.Embodiments of the invention are not mutually exclusive, but may beimplemented in various combinations. The described embodiments of theinvention and the disclosed examples are given for the purpose ofillustration rather than limitation of the invention as set forth theappended claims.

It has now surprisingly been found that it is possible to obtain ahigher inhibition of ADP induced platelet aggregation with faster onset,which will ameliorate one or more of the drawbacks of clopidogrel. Thepresent invention meets the long felt need in the treatment ofthrombosis and embolism and associated disease conditions. The variousaspects of the invention are described in detail with specificembodiments/conditions hereafter.

In accordance with one aspect, the invention provides methods for thetreatment and/or prophylaxis of thrombosis and/or embolism, as well ascompositions for use in such methods, wherein the method comprisesadministering an isolated (S)-isomer of thiolactone compound of FormulaII (also referred to herein as (S)-oxo-clopidogrel or (S)-oxo metaboliteof clopidogrel or (S)-thiolactone) or a derivative thereof in its freeform or a pharmaceutically acceptable salt thereof. This results in thein vivo formation of the active metabolite of clopidogrel at aconcentration greater or equivalent to the concentration of activemetabolite obtained by adminitration of clopidogrel wherein the dose ofsaid thiolactone or derivative is substantially lower than acorresponding dose of clopidogrel. Preferably the dose of thiolactone(oxo-clopidogrel) or its derivative is lower by two times, morepreferably lowered by about 3 times, still preferably lowered by about 5times and still preferably lowered by about 10 times or more. Forexample, a dose of the primary active principle of the present inventionof 20 to 40 mg, 35 to 80 mg or 50 to 100 mg will provide an improvedtherapeutic effect or a higher in vivo concentration of the activemetabolite of clopidogrel than that observed following a dose of 300 mg,600 mg or 900 mg of clopidogrel, respectively. Similarly, a dose of theprimary active principle of the present invention of 5 to 15 mg or 6 to30 mg will provide an improved therapeutic effect or a higher in vivoconcentration of the active metabolite of clopidogrel than that observedfollowing a dose of 75 mg or 150 mg of clopidogrel, respectively.Accordingly in the present invention, the active metabolite activityobtained is greater or equivalent to clopidogrel at a dose substantiallylower than administration of clopidogrel.

It should be understood that thiolactone compound of Formula II existsin tautomeric form of the Formula IIA and the tautomers may be employedin the methods and compositions of the present invention. Derivatives ofthe thiolactone compound include, but are not limited to, esters orsilyl ethers, wherein the hydroxyl group of the compound of Formula IIAis derivatized. The derivatized group is preferably hydrolizable in vivoby esterases after administration. The preferred ester groups are alkyl(straight chain or branched chain) or aryl esters, more preferably anacetyl or n-butyl/t-butyl esters as expressed in Formula IIA.

The present invention permits the dose of active ingredient required forachieving a therapeutic effect to be reduced compared withadministration of clopidogrel. The compounds of Formula II or IIA can beadministered as their acid/base addition salts and since the weight ofaccompanying acid/base changes from one to another, the dose may becalculated based on free thiolactone or its derivative. The dosesdiscussed herein are for a patient of 60 kg average body weight. Itshould be understood that dose may be adjusted with respect to bodyweight of the patient, health/condition condition of the patient,severity of the disease, metabolic profile of the compounds of thepresent invention. The skilled person in the art has the ability andexpertise to adjust the dosage as required.

The inventive selection of the compounds of Formula II or IIAsignificantly contributes to improvements in the antiplatelet treatmentcompared to the use of clopidogrel and improves its therapeuticefficiency by about 5-15 times as well as reducing the associatedtoxicity/side effects or metabolic load associated with clopidogreltreatment.

The present invention can provide a therapeutically effectiveconcentration of active metabolite of clopidogrel in a short time afteradministration, which not only improves the onset of action but alsoachieves greater than 50% inhibition of ADP induced plateletaggregation. The onset of action can be (as measured by 50% inhibitionof ADP induced platelet aggregation) achieved in less than 1 hour, morepreferably in 30 minutes, compared to 4-6 hours for clopidogrel.Irrespective of the dose of compounds of Formula II or IIA, the maximumplatelet aggregation can be achieved in less than 1 hour after oraladministration. This invention thus ameliorates the dose ceiling effectobserved with higher doses of clopidogrel and provides significantlyhigher metabolic output and reduced metabolic loading in liver.Furthermore, as clopidogrel is a P-Glycoprotein (Pgp) substrate, itsabsorption is influenced by Pgp inhibitors or inducers, which are likelyto alter the clinical effects of clopidogrel. This effect should also bereduced to a large extent by the administration of the compositions ofthe present invention. Additionally, the invention may permit the use ofproton pump inhibitors in combination with clopidogrel. It is believedthat this is because the role of CYP2C19 (which plays a significant partin the metabolism of clopidogrel) is reduced substantially with the useof the compositions and methods of the present invention, PPIs beinginhibitors of CYP2C19.

According to aspects of the present invention, an initial loading doseof between 20-100 mg of compound of Formula II or its derivative(Formula IIA) or a salt thereof may be administered to a human subjectin need of treatment or prophylaxis of vascular embolism or thrombosisand, if necessary, a maintenance dose as low as 5-40 mg may beadministered such that the concentration of active metabolite ofclopidogrel in human plasma is greater than that observed when a loadingdose of 300-900 mg and maintenance dose of 75-150 mg of clopidogrel areadministered. Preferably a dose of 40-60 mg of the thiolactone compoundof Formula II/IIA will achieve greater than 50% inhibition of ADPinduced platelet aggregation within an hour, and a maintenance dose ofabout 6-25 mg is sufficient to maintain platelet inhibition at or abovethe desired level during the maintenance period. It should, however, benoted that dose adjustments may be made based on the body weight of thepatients, which should not be considered to limit the invention.

Apart from increasing the active metabolite concentration and achievinggreater platelet inhibitory activity, the compositions and methods ofthe present invention are thought to reduce the toxicity and/orassociated side effects observed due to the formation of clopidogrelacid (Formula IV) following clopidogrel administration. The lethal doseof clopidogrel is about 5000 mg per kg in rat and 90% of clopidogrel isconverted to clopidogrel acid in vivo. Thus, it appears that around 90%of the toxicity of clopidogrel may be related to the clopidogrel acidmetabolite (Formula IV). Given that the compositions and methods of thepresent invention advantageously enable the amount of active ingredientadministered to patients to be reduced, while also eliminating theformation of clopidogrel acid metabolite following administration, theassociated toxicity or adverse side effects will be reduced by at least9-10 times compared to current clopidogrel therapeutic use.

The compounds employed in the compositions and methods according topresent invention are preferably present in the form of theirpharmaceutically acceptable salts, preferably acid salts. Examples ofsuch acid addition salts include salts with mineral acids, especiallyhydrohalic acids (such as hydrofluoric acid, hydrobromic acid,hydroiodic acid or hydrochloric acid), nitric acid, carbonic acid,sulfuric acid or phosphoric acid; salts with lower alkylsulfonic acids,such as methanesulfonic acid, trifluoromethanesulfonic acid orethanesulfonic acid; salts with arylsulfonic acids, such asbenzenesulfonic acid or p-toluenesulfonic acid; and salts with organiccarboxylic acids, such as acetic acid, propionic acid, butyric acid,fumaric acid, tartaric acid, oxalic acid, malonic acid, maleic acid,malic acid, succinic acid, benzoic acid, mandelic acid, ascorbic acid,lactic acid, gluconic acid or citric acid. Salts, which are notpharmaceutically acceptable may also be employed in the manufacture ofthe compounds employed in the methods and compositions according to theinvention. Preferred salts include hydrochloride, hydrogen sulphate andmaleate salts.

The methods and compositions of the present invention may further employone or more active compounds including antiplatelet agents such asaspirin, cilostazol, dipyridamole and the like which may operate by amechanism similar or different to the clopidogrel active metabolite toachieve desired levels of anti-platelet activity. The second orsubsequent anti-platelet agent may be administered separately,simultaneously or subsequently with the compound of Formula II or itstautomer or a derivative thereof in its free form or as apharmaceutically acceptable salt thereof. The present inventionencompasses such modifications thereof for achieving desired goal ofinhibition of platelet aggregation.

In other aspects, the present invention provides a fixed dosepharmaceutical composition of compound of Formula II or its tautomers orits derivative of Formula IIA or a pharmaceutically acceptable saltsthereof wherein the dose of said thiolactone is selected from the rangeof 5 mg to 35 mg and the composition optionally comprisespharmaceutically acceptable excipients. The fixed dose composition ofthe present invention may comprise or be administered along with one ormore active compounds including antiplatelet agents such as aspirin,cilostazol or the like which may operate by a mechanism similar ordifferent to the clopidogrel active metabolite.

The fixed dose pharmaceutical compositions of the invention arepreferably administered orally on a daily basis as an immediate releaseor modified release dosage form.

The dosage form may be formulated as a single unit dosage, as twoseparate unit dosages, and/or in any of the many variations known in theart, which include, but are not limited to, tablets, pills, hardcapsules, soft capsules, pharmaceutical sachets and powders forreconstitution.

The formulations of the invention may further contain water insolublepermeable polymers, herein defined as “modified release polymers”, toadjust their release profile. These polymers may either be coated ontoformulations such as tablets, microgranules, capsules or pills, or bemixed together with the other ingredients of any of the formulationslisted above.

In one embodiment, the pharmaceutical compositions of the presentinvention are provided in the form of tablets prepared by mixing theactive agents with excipients. Typical excipients include diluents,fillers, binders, lubricants, disintegrants, glidants, colorants,pigments, taste masking agents, modified release polymers, sweeteners,plasticizers, and any acceptable auxiliary substances such as absorptionenhancers, penetration enhancers, surfactants, co-surfactants, andspecialized oils. Examples of excipients include calcium phosphates,such as dibasic calcium phosphate, anhydrous dibasic calcium phosphate,tribasic calcium phosphate, etc.; microcrystalline cellulose, powderedcellulose; starch, pre-gelatinized starch; sodium starch glycolate;dextrates; mannitol, sorbitol; povidone; ethyl cellulose; lactose;kaolin; silicic acid; lubricants such as magnesium stearate, calciumstearate, stearic acid, mineral oil, glycerin, sodium lauryl sulfate,polyethylene glycol; and/or talc. Sodium starch glycolate, talc and thelubricant magnesium stearate may be used to prepare compositions of thepresent invention to aid in tablet manufacture. A premix of compound ofFormula II/IIA may be obtained by mixing said compound with ingredientsand thereafter either directly compressing the mixture into tablets orfilling said mixture into capsules optionally along with other suitableingredients to obtain final dosage form. A unit dose of the free form ofa compound of Formula II/IIA may be obtained as a granular premix bysuitably processing that compound with acceptable ingredients such aspolymers, which can be directly compressed or formulated with additionalexcipients.

The compositions and methods of the present invention may be employed inthe prevention and/or treatment of pathological states such as disordersof the cardiovascular and cerebrovascular system such as thethromboembolic disorders associated with atherosclerosis or withdiabetes such as unstable angina, cerebral attack, restenosis followingangioplasty, endarterectomy or fitting of metallic endovascularprostheses, with rethrombosis following thrombolysis, with infarction,with dementia of ischaemic origin, with peripheral arterial diseases,with haemodialyses, with auricular fibrillations or during the use ofvascular prostheses or aortocoronary bypasses or in relation to stableor unstable angor.

The compounds of Formula II or its acid salts can be obtained by anymethod disclosed in U.S. Pat. Nos. 4,740,510 and 5,190,938, which areincorporated herein by reference, for its various ester derivatives.Chiral isomer separation may be performed by any known racemicseparation method using chiral acids or the isomer may bestereo-selectively synthesized.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the followingillustrative examples, make and utilize the compounds of the presentinvention and practice the claimed methods. The following examples aregiven to illustrate the present invention. It should be understood thatthe invention is not to be limited to the specific conditions or detailsdescribed in those examples.

Example 1 (±)-Thiolactone Compound of Formula II

10.43 g potassium bicarbonate, 7.852 g sodium iodide and 11 gmmethyl-2-bromo-2-(chlorphenyl acetate were added to a solution of 10 gmof 5,6,7,7a-tetrahydro-4H-thieno[3,2-c]pyridine-2-one hydrochloride in100 ml dimethylformamide. The medium is heated to 60° C. for 2 hours andthen poured into 600 ml water. The product is extracted using ethylacetate.

Example 2 Methyl-(R)-2-hydroxy-2-(2-chlorophenyl)acetate

In a 1 L flask, 120 g (0.643 mole) of (R)-2-chloromandelic acid, 480 mlmethanol and 4.8 g concentrated sulfuric acid were added. The solutionis then heated to reflux for 2 hours and excess methanol is distilledunder vacuum. The oily residue was taken in 650 ml chloroform and washedwith 240 gm aqueous solution of 10% potassium carbonate and concentratedunder vacuum. 124.4 gm of methyl-(R)-2-hydroxy-2-(2-chlorophenyl)acetatewas obtained in the form of a colorless oil.

Example 3Methyl(R)-2-(4-nitrophenylsulfonyloxy)-2(2-chlorophenyl)acetate

0.72 g (6 mmoles; 0.1 equivalent) of 4-dimethylaminopyridine, 12.0 g (60mmoles; 1 equivalent) of methyl(R)-2-hydroxy-2(2-chlorophenyl)acetateand 7.8 g (78 mmoles; 1.3 equivalent) of triethylamine and 20 ml ofdichloromethane were added to a dry reaction flask. The colorlesssolution obtained was cooled to 0° C. and then, operating at thistemperature, 13.14 g (60 mmoles; 1 equivalent) of 4-nitrobenzenesulfonylchloride as a solution in 30 ml of dichloromethane was added. Thereaction mixture was stirred for 3 hours at 0° C. and 240 ml of 1Nhydrochloric acid and 240 ml of dichloromethane was added drop wise,while stirring this mixture. After decanting, the dichloromethane phaseis washed with dilute hydrochloric acid and then with water, beforebeing concentrated under reduced pressure. An analytically pure sampleis obtained after purifying on a silica column. In this manner,methyl(R)-2-(4-nitrophenylsulfonyloxy)-2(2-chlorophenyl)acetate isobtained: Yield: 98%. Optical purity: 99%.

Example 4Methyl(S)-2(2-chlorophenyl)-2-(2,4,5,6,7,7a-hexahydrothieno[3,2-c]-5-pyridin-2-one)acetate

In a dry, 50-ml reaction flask, 5 mmoles of5,6,7,7a-tetrahydro-4H-thieno[3,2-c]pyridin-2-one as a solution 7.5 mlof dichloromethane (prepared from hydrochloride salt afterneutralization with aq. potassium carbonate) and 2.85 g of a 30% aqueoussolution of potassium carbonate were mixed. After stirring for 10minutes, 5 mmoles of theMethyl(R)-2-(4-nitrophenylsulfonyloxy)-2(2-chlorophenyl)acetate as asolution in 2.5 ml of dichloromethane was added. The two-phase mediumthus obtained was heated under reflux for 1 hour and then cooled to 7°C. and decanted. After work-up, (S)-isomer of titleMethyl(S)-2(2-chlorophenyl)-2-(2,4,5,6,7,7a-hexhydrothieno[3,2-c]-5-pyridin-2-one)acetate[(S)-thiolactone of Formula II] was obtained. Optical purity (2′S)>98%.

Example 5Methyl(S)-2(2-chlorophenyl)-2-(2,4,5,6,7,7a-hexahydrothieno[3,2-c]-5-pyridin-2-one)acetate

In a dry, 250-ml reaction flask, 5.94 gm (31.1 mmoles) of5,6,7,7a-tetrahydro-4H-thieno[3,2-c]pyridin-2-one hydrochloride, 39 mlof dichloromethane and 29.8 g of a 30% aqueous solution of potassiumcarbonate were mixed. After stirring for 10 minutes, 10 gm of (25.9mmoles ofMethyl(R)-2-(4-nitrophenylsulfonyloxy)-2(2-chlorophenyl)acetate as asolution in 13 ml of dichloromethane was added. The two-phase mediumthus obtained was heated under reflux for 6 hrs. Then cooled to about30° C. Filtered the R.M. Filtrate was having two layers. MDC layer waswashed with brine solution. Dried over anhydrous sodium sulfate. AfterconcentrationMethyl(S)-2(2-chlorophenyl)-2-(2,4,5,6,7,7a-hexhydrothieno[3,2-c]-5-pyridin-2-one)acetate[(S)-thiolactone of Formula II] was obtained.

Example 6 Acetyl Ester of Compound of Formula II

83.85 g of (S)-thiolactone compound of formula II obtained above wasdissolved in 120 ml of isopropenyl acetate and mixed with 7.8 g ofp-toluene sulfonic acid. The mixture is heated to 90° C. under stirringfor 6 hours. The reaction mass then cooled to about 20° C. and 20 ml ofwater was added to the mixture. The mixture is then basified by additionof saturated aqueous sodium bicarbonate solution and extracted withethyl acetate. Ethyl acetate layer is further washed twice with waterand distilled under vacuum to remove ethyl acetate. The residue obtainedwas dissolved in acetone and HCl gas was passed into the solution undercooling. The obtained precipitate was filtered, recrystallized fromacetone to get hydrochloride salt of acetyl derivative. Opticalpurity>99.5%

Example 7 Acetyl Ester of Compound of Formula II

25 g (74 mmole) of (S)-thiolactone compound of formula II was taken in250 ml of acetonitrile. The mixture was cooled. Then added 9.03 gm (95.1mmole) of triethylamine under stirring followed by addition of 9.11 gm(95.1 mmole) of acetic anhydride under cooling. After addition reactionmass was stirred at ambient temperature. Then distilled offacetonitrile. Residue was dissolved in ethylacetate, washed with waterand concentrated. The residue obtained was dissolved in isopropanol.Added 1 mole equivalent of isopropanol.HCl solution. The obtainedprecipitate was filtered to get hydrochloride salt of acetyl derivative

Example 8 Pharmacology and Toxicology

The pharmacological and toxicological results which are reported belowdemonstrate the properties of the compositions of the invention bothfrom the point of view of toxicity and tolerance, and from the point ofview of their activities, particularly inhibition of platelet andthrombotic aggregation.

A. Toxicological Study

The compositions of the invention demonstrate excellent tolerance andlow toxicity. In addition, the tests carried out on the acute, chronic,subchronic and delayed toxicities in different species of animals, havenot demonstrated any local or general reaction, disturbance or anomalyin the biochemical, macroscopic or microscopic examinations carried outduring these experiments.

B. Pharmacological Study

The platelet aggregation inhibiting activity and the toxicity of theinventive compositions were compared to those of the clopidogrel asdescribed in the French Pat. No. 82,12599 (Publication No. 2 530 247),which is incorporated herein by reference.

The platelet aggregation inhibiting activities and the antithromboticactivities of the compounds were studied in the rat by standard methods.

1. Measurement of Platelet Aggregation with ADP

The activity on the aggregation of plates induced by ADP or collagen wasdetermined ex-vivo.

The products dissolved in ethanol (200 mg/ml) and diluted in watercontaining gum arabic (5%-wt/v) were administered by the oral route togroups of five female rats of the CD-COBS strain, weighing 250-300 g, inamounts of 10 ml of suspension per kilogram two hours before bloodsamples were taken.

The blood samples were taken from animals anesthetized with diethylether by puncture of the abdominal aorta and placed over a 3.8% aqueoussolution of sodium citrate (1 vol/9 volumes of blood). The platelet-richplasma was then isolated by centrifugation at 200 g for 10 minutes.

Aggregation is induced by the addition of 2 μl of aggregating solutionto 400 μl of platelet-rich plasma. The aggregating solutions used were:a 500 μM aqueous solution of ADP (final concentration 2.5 μM).

The aggregation of the platelets was monitored as described by Born(Nature 194, p. 927 (1967)), which is incorporated herein by reference,using a Coultronics® aggregometer at a temperature of 37° C. andagitation of 900 rpm.

For aggregation with ADP, the aggregometer generates a curverepresenting a platelet aggregation as measured by a change in opticaldensity. The height of this curve is defined as the height ofaggregation. The percentage of aggregation is the relation between theaggregation height measured and the height corresponding to 100%aggregation×100. The percentage of inhibition is determined by therelation:

$\frac{{{Control}\mspace{14mu} {aggregation}\mspace{14mu} {height}} - {{produced}\mspace{14mu} {aggregation}\mspace{14mu} {height}}}{{Control}\mspace{14mu} {aggregation}\mspace{14mu} {height}} \times 100$

The results obtained for the aggregation with ADP are shown in Table 1and they demonstrate that activity of the molecule. The controls arewithout drug.

TABLE 1 Qty of base Dose administered % Product (mg/kg) (mg/kg)aggregation* % inhibition P** Control 103 ± 3  Clopidogrel 12.5 9.613 19± 4 82 0.001 bisulphate 25 19.225 11 ± 1 89 0.001 Control 94 ± 1Thiolactone 2.5 2.5  4 ± 2 95 0.001 *height, Mean of results ± standarddeviation **Students test

2. Anti-Thrombotic Activity

The antithrombotic activity has also been studied in the test of venousthrombosis on a screw thread described by Kumada T. et al. in Thromb.Res 18 p. 189 (1980).

Female rats of the same type as those previously described, in groups of10 animals, were anesthetized with diethyl ether and their vena cava wasisolated after abdominal incision.

A metallic screw thread 21 mm long consisting of a dentist's drill,marketed by Dyna (France) size No. 30, was introduced into the lumen ofthis vein just below the renal bifurcation descending towards the iliacveins, without damaging the wall; 19 to 20 mm of the length of the screwthread are implanted and the remaining 1 mm protrudes through the closedstomach into the exterior.

The thrombi formed rapidly and five hours later, under pentobarbitalanesthesia, the abdomen is reopened and ligatures are placed above andbelow the screw thread which is withdrawn after longitudinal incision ofthe vein and the isolated thrombus is weighed.

The results which are presented in Table 2 show that thiolactone ofFormula II is superior to clopidogrel. The control is without drug.

TABLE 2 Qty of base Weight of Dose administered thrombus* % Product(mg/kg) (mg/kg) (mg) inhibition P** Control 3.9 ± 0.3 Clopidogrel 107.69 1.26 ± 0.19 67 0.001 bisulphate 20 15.38 1.20 ± 0.13 69 0.001control 4.18 ± 0.31 Thiolactone 12.5 12.5 1.18 ± 0.18 76 0.001 *Mean ofresults ± standard deviation; **Students test

Although certain presently preferred embodiments of the invention havebeen specifically described herein, it will be apparent to those skilledin the art to which the invention pertains that variations andmodifications of the various embodiments shown and described herein maybe made without departing from the spirit and scope of the invention.Accordingly, it is intended that the invention be limited only to theextent required by the appended claims and the applicable rules of law.

What is claimed is:
 1. A method for reducing or alleviating interindividual platelet response variability and metabolic loading in humanin the treatment and/or prophylaxis of thrombosis and/or embolismsobserved following administration of an anti-platelet drug comprisingadministering to a person in need thereof, a composition containing aneffective amount of S-oxo-clopidogrel or its derivatives of Formula IIA

or a pharmaceutically acceptable salt, wherein R is hydrogen or ahydrolysable group.
 2. The method of claim 1, wherein the method furthercomprises administering one or more anti-platelet agent selected fromthe group consisting of aspirin, cilostazol and dipyridamole.
 3. Themethod of claim 1, wherein the inter-individual variability is due to aCYP450 polymorphism or a failure to efficiently metabolize clopidogrel.4. The method of claim 3, wherein the CYP450 polymorphism is CYP2C19*2or CYP2C19*17.
 5. The method of claim 1, wherein the inter-individualvariability due to P-glycoprotein efflux transports.
 6. The method ofclaim 1, wherein said method avoids or alleviates the side effectsassociated with the clopidogrel acid metabolite of Formula IV


7. The method of claim 1, wherein the method achieves a therapeuticeffect greater or equivalent to that observed following theadministration of a substantially higher dose of clopidogrel.
 8. Themethod of claim 1, wherein said method results in the in vivo formationof the active metabolite of clopidogrel at a concentration greater thanor equivalent to that observed following administration of asubstantially higher dose of clopidogrel.
 9. The method claim 1, whereinthe onset of therapeutic action is at least 50% more rapid than thatobserved following administration of a substantially higher dose ofclopidogrel.
 10. The method of claim 1, wherein the amount of the(S)-oxo-metabolite or its derivative of Formula IIA is about 20 to about100 mg as a loading dose.
 11. The method of claim 1, wherein the amountof the (S)-oxo-metabolite or its derivative of Formula IIA is about 35to about 70 mg as a loading dose.
 12. The method of claim 1, wherein theamount of the (S)-oxo-metabolite or its derivative of Formula IIA isabout 20 to about 100 mg as a loading dose.
 13. The method of claim 1,wherein the amount of the (S)-oxo-metabolite or its derivative ofFormula IIA is about 5 to about 30 mg as a maintenance dose.
 14. Themethod of claim 1, wherein the amount of oxo-metabolite or itsderivative of Formula IIA is about 6 to about 20 mg as a maintenance.15. The method of claim 1, further comprising administering a protoninhibitor.
 16. The method of claim 1, wherein the administration stepcomprises an initial loading dose of about 20-100 mg of the(S)-oxo-clopidogrel or its derivative of Formula IIA is administered tothe person, followed by a maintenance dose of about 5-30 mg.
 17. Acomposition comprising (S)-oxo-clopidogrel or its derivative of formulaIIA

or a pharmaceutically acceptable salt thereof, wherein R is hydrogen ora hydrolysable group; and an excipient.
 18. The composition of claim 17,further comprising a proton pump inhibitor.
 19. The composition of claim17, further comprising an anti-platelet agent selected from the groupconsisting of aspirin, cilostazol and dipyridamole.
 20. A fixed dosecomposition of (S)-oxo-clopidogrel or its derivative of Formula IIAcharacterized in that said composition comprises a dose of 5-35 mg ofoxo-clopidogrel or its derivative of Formula IIA and a pharmaceuticallyacceptable excipient.
 21. The composition of claim 20, furthercomprising an anti-platelet agent selected from the group consisting ofaspirin, cilostazol and dipyridamole; and/or a proton pump inhibitorcompound.